USGS Professional Paper 1697 - Alaska Resources Library

270 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
Cache Creek terrane. Inferred reserves are 227,000 tonnes
grading 6.86 g/t Au (Madu and others, 1990). The Lust Dust
Au-Ag-Zn-Sb deposit consists of veins and replacements composed
of quartz-stibnite-boulangerite-sphalerite-pyrite. The
veins and replacements occur in a shear zone in folded sedimentary
rocks of the Cache Creek terrane (Armstrong, 1949).
The Indata Lake Au-Ag prospect is composed of quartz-pyritearsenopyrite-chalcopyrite-stibnite
veins that occur in sheared
and brecciated volcanic rocks of the Takla Assemblage and
limestone of the Cache Creek terrane (Eastfield Resources
Ltd., News Releases of October, 28, November 4, December
1, 1987). The deposit and sheared rocks occur along a splay of
the Pinchi Fault.
Origin of and Tectonic Controls for Pinchi Lake
Metallogenic Belt
The deposits in the Pinchi metallogenic belt postdate the
host bedrock units, both the Late Triassic blueschist of the
Cache Creek terrane and overlying Late Cretaceous and early
Tertiary conglomerate (Paterson, 1977). The deposits occur
in shears along the Pinchi Fault, which separates the Mississippian
to Triassic Cache Creek terrane from the Late Triassic
Quesnellia island-arc terrane. The fault is interpreted as
providing a zone of permeability for mercury-bearing hydrothermal
solutions (Dawson and others, 1991). Reactivation and
shearing along the fault and formation of the deposits may have
occurred during a period of uplift, magmatism, and transcurrent
faulting in the Eocene and Oligocene (Gabrielse, 1985), possibly
related to the Cascade volcanic-plutonic belt to the south.
No known Eocene or Oligocene intrusions exist in the region.
Owl Creek Metallogenic Belt of Porphyry Cu-Mo,
Porphyry Mo, and Au Polymetallic Vein Deposits
(Belt OC), Southern British Columbia
The Owl Creek metallogenic belt of porphyry Cu-Mo,
porphyry Mo and Au polymetallic vein deposits (fig. 103; tables
3, 4) occurs in southern British Columbia and is associated
with a belt of late Tertiary plutons that extends from northern
Washington into the Coast Plutonic Complex. The plutons are
mostly small, circular quartz monzonite to dioirite plugs that
intrude major, northwest-trending shear zones. These granitoid
rocks are part of the middle Tertiary to Recent Cascade
continental-margin arc, which occurs in the United States
Pacific Northwest and southern British Columbia (Nokleberg
and others, 1994c, 1997c; Monger and Nokleberg, 1996). The
significant deposits in the belt are the Owl Creek district porphyry
Cu-Mo deposits, and the Clear Creek (Gem) porphyry
Mo deposit (table 4) (Nokleberg and others 1997a,b, 1998).
The deposits in the Owl Creek metallogenic belt are hosted in
or near (1) calc-alkaline, high-level plutons of the Chilliwack
suite that is part Chilliwack Batholith on the British Columbia-Washington
border, and (2) the Doctor’s Point pluton on
Harrison Lake that is coeval and probably cogenetic with the
Pemberton belt of late Tertiary volcanic rocks (Souther, 1991;
Woodsworth and others, 1991). The significant deposits are
at: Clear Creek (Gem), Owl Creek district, and Salal Creek.
Lesser deposits occur at Harrison Gold (Abo) and Doctor’s
Point. These mesothermal Au polymetallic vein deposits are
intimately associated with 25-Ma quartz diorite intrusions and
either consist of veins in hornfels adjacent to the stock, as at
Doctor’s Point, or as vein stockworks within the quartz diorite
pluton, as at Harrison Gold (Ray, 1991). The veins contain
quartz, pyrrhotite, and pyrite, and minor chalcopyrite, molybdenite,
scheelite, and rare bismuth telluride minerals (Dawson
and others, 1991). Also occurring in the metallogenic belt are
Au polymetallic vein deposits at Boundary Red Mountain and
Lone Jack mines, which are located along the western part of
the Chilliwack Batholith in Washington (Ray, 1986).
Clear Creek (Gem) Porphyry Mo Deposit
The Clear Creek (Gem) porphyry Mo deposit consists of
an arcuate zone of molybdenite with minor pyrite and sphalerite
that occur in quartz and calcite veins and as fracture filling
(EMR Canada, 1989; MINFILE, 2002). Estimated reserves are
15.9 million tonnes grading 0.07 percent Mo (MINFILE, 2002).
The deposit occurs in an arcuate zone around the northeast margin
of an Oligocene quartz monzonite stock, named the Gem
Stock, with a K-Ar isotopic age of 35 Ma. The stock intrudes
quartz diorite and granodiorite of the mid-Cretaceous Spuzzum
pluton, and schist and gneiss of the Cretaceous Settler Schist.
Owl Creek Porphyry Cu-Mo District
The Owl Creek porphyry Cu-Mo district consists of veins
and disseminations of chalcopyrite, molybdenite, and pyrite
with minor bornite that occur as blebs, disseminations, and fracture
fillings (Mahoney, 1977; EMR Canada, 1989; MINFILE,
2002). Estimated resources are 10 to 20 million tonnes grading
0.3 to 0.4 percent Cu and 0.03 percent MoS 2 (MINFILE, 2002).
The deposit is hosted in probable mid-Tertiary quartz diorite and
feldspar porphyry of the Coast Plutonic Complex and in propylitic-
and argillic-altered and volcanic rocks of the Late Triassic
Cadwallader Group (Mahoney, 1977).
Salal Creek Porphyry Mo Deposit
The Salal Creek porphyry Mo deposit occurs along the
contact between a fine-grained granite core and a mediumgrained
granodiorite margin of a pluton dated that has a K-Ar
isotopic age of 8 Ma (Stephens, 1972). The deposit exhibits in
a typical ring or circular pattern. To the north is the Franklin
Glacier porphyry Cu-Mo prospect, which has a K-Ar isotopic
age of 7 Ma (Dawson and others, 1991).
Origin of and Tectonic Controls for Owl Creek
Metallogenic Belt
The Owl Creek metallogenic belt of porphyry Cu-Mo,
porphyry Mo and Au polymetallic vein deposits is hosted in a